Five ml heparinized whole blood will be drawn for QFT-G before for PPD testing. The blood specimens will be incubated for 16-20 h (overnight) at 37°C in a humidified atmosphere. IFN-γ levels in the nil well will be considered background and will be subtracted from the results of the mitogen well and the antigen-stimulated wells. The results will be considered positive if the concentration of.IFN-γ in the sample well after stimulation with ESAT-6 and/or CFP-10 will be greater than or equal to 0.35 IU/ml (after subtracting the value of the nil well), regardless of the results of the positive control (mitogen well). The results will be considered negative if the response to the specific antigens (after subtracting the value of the nil well) is less than 0.35 IU/ml and if the IFN-γ levels of the positive control (after subtracting the value of the nil well) is greater than or equal to 0.5 IU/ml. The results will be considered indeterminate if both antigen-stimulated sample wells are negative (i.e., <0.35 IU/ml after subtracting the value of the Nil well) and if the value of the positive control well is less than 0.5 IU/ml after subtracting the value of the nil well